Hydraulic or hydropneumtic shock absorber or telescopic suspension, equipped with built-in compensator, habing small overall dimensions, easy to carry out and highly reliable

ABSTRACT

The compensator consists of at least one flexible and preferably elastic braiding ( 8 ), fitted up outside onto the cylinder ( 1 ) of the shock absorber, seal-fastened with its own ends onto said cylinder by means of suitable fastening means ( 19, 10 ) and carried out in such a way as to contain a chamber with variable volume (C) occupied by oil and communicating with at least one of the inside chambers of the shock absorber, for instance with the chamber with the larger volume, by means of holes provided on said cylinder.

DESCRIPTION

[0001] The present invention relates to shock absorbers and totelescopic suspensions. In general, both hydraulic and hydropneumatic,equipped with a compensator to compensate the various volume changes inthe chambers placed opposite the piston in the telescopic system whenone of such chambers is occupied by a stem fastened to the piston of thetelescopic system. The compensator is connected to one of the insidechambers of the telescopic system, usually to the one with the largervolume. In some cases compensators are mounted at the interior and onthe It bottom of said chamber with the larger volume, thus increasingthe overall length of the telescopic system, and more often they areplaced outside, laterally or even in a distant position from thetelescopic system itself, with a flexible pipe representing theconnection to said chamber with the larger volume.

[0002] Compensators of the known type substantially consist of a chamberdivided into two portions by a piston with lateral seal, or by amembrane made of flexible and possibly elastic material, one portion ofsaid chamber being full of oil and connected to the chamber with thelarger volume of the telescopic system, the other chamber portion isusually occupied by a pressurized gas, whose pressure is oftenadjustable, so as to ensure a rapid return of the oil from thecompensator back to the inner circuit of the telescopic system when thelatter is making the extension stroke, also to avoid cavitationphenomena within said circuit. From above it results that compensatorsof the known type substantially involve a problem of space and theynormally require a pressurizing chamber opposite to the one occupied bythe oil.

[0003] The present invention aims at overcoming these and otherdisadvantages from the known art by means of the following solutionidea. At least one tubular, flexible and preferably elastic, impermeableand oil-resistant braiding is fitted up on the outside lateral surfaceof the cylinder in the telescopic system, said braiding beingseal-fastened with its ends onto said cylinder, for instance by means ofbands or other suitable means, so as to form at its interior acompensation chamber with changing volume itself, said chamber beingconnected to at least one of the inner chambers of the telescopicsystem, for instance to the chamber with the larger volume, by means ofholes on the ends of said chamber. The compensator thus obtainedpresents extremely limited overall dimensions and does not require apressurization from outside since its emptying is substantially helpedby the elastic memory of the braiding which forms same.

[0004] Further features of the present invention and the advantagesderiving from them will become more evident from the followingdescription of some preferred embodiments of said invention, shown as amere non-limiting example in the figures of the two drawing tablesenclosed where:

[0005]FIG. 1 shows a schematic longitudinal section of a shock absorberequipped with the compensator according to the present invention;

[0006]FIGS. 2 and 3 show possible outside structures of the wallsupporting the elastic braiding of the compensator;

[0007]FIGS. 4 and 5 show a longitudinal section, divided into twoportions, of a fork leg, particularly suitable for the so-calledmountain bikes or for other two-wheel vehicles.

[0008] In FIG. 1 the numeral 1 indicates the cylinder of a shockabsorber, closed at one end containing a piston 2 connected to a stem 3which comes out of the other end of the cylinder 1 axially and with alateral seal, said piston with a lateral seal sliding within thecylinder. The numerals 4 and 5 indicate the connection points for theshock absorber to the two points of the mechanism to be cushioned, saidpoints being usually stressed through reciprocal distancing using anelastic means, which is not shown here, so that the shock absorber inits rest position has its stem 3 extending from the cylinder 1. Theinside chambers A and B of the cylinder 1, defined by the opposite sidesof the piston 2, are full of oil or any other suitable liquid, and onthe piston 2 valves of any suitable type are supplied, which may also bedifferent from those shown in the schematic with the numeral 5, saidvalves being possibly adjustable and able to control the passage of oilbetween chambers A and B during the extension and retraction stroke ofthe stem 3, so as to ensure the necessary cushioning of the stresses towhich the telescopic unit of the present invention is subjected.

[0009] In order to compensate for the various volume changes in thechambers A and B, said chamber A being larger in volume than chamber Bsince it is not occupied by the stem 3, the present invention provides,for example, for lateral openings 7 in correspondence to the base of thechamber with the larger volume A and, mounted on the outside of thecylinder 1, a water tight sock 8, said sock being flexible andpreferably made of any suitable, elastomeric and oil-resistant material,of a suitable length and thickness and being self-fastened by its ownends onto the cylinder 1, for instance with centripetal tighteningmethods 9 and 10, for instance with clamps or groups of cone-shapedrings with different hardness, whose contact surfaces are equipped withanti-unthreading stripes (FIG. 3), similar to those which are used forthe reciprocal seal-connection of pipes within hydraulic circuits, sothat said sock 8 and the outside wall of the cylinder 1 onto which saidsock is placed, together form a compensation chamber C sealed towardsthe outside, which can change in volume due to the flexibility andelasticity of said sock 8 and which communicates with the chamber A ofthe shock absorber through the openings 7. In order to ensure a correctclosure of the ends of the braiding 8, its own ends of the braidingand/or the portions of it touching the cylinder 1 or the tighteningmethods 9, 10 can be shaped in any suitable way. The chamber C is alsofull of oil. In particular, when the stem 3 is in its extended or restposition, the chamber C shows the smallest volume. When the stem 3 isstressed by retraction, the oil partly flows from chamber A to chamber Bthrough the valve system 6 of the piston 2 and the surplus flows intothe compensation chamber C through the openings 7. This oil will thenreturn to the chamber A when the stem 3 makes its extension stoke. Atthis latter stage, the oil must freely flow into the chamber A withoutcausing cavitation phenomena, and this is prevented by the elasticitymemory of the sock 8 and the wide passage formed by the openings 7.

[0010] To ensure the free flow of oil between the chambers A and C, itis by preference foreseen that the openings 7 open into an outsidering-shaped recess 107 of the cylinder 1 and it can also be foreseenthat small grooves would open in such a recess, said grooves taking upthe whole length or part of the outside surface of the cylinder 1forming said chamber C, for example small rectilinear grooves 11 asshown in FIG. 2 or small helicoidal grooves 12 as shown in FIG. 3. Thelongitudinal grooves 11 or 12 can also be forecast onto an intermediateportion of the inside lateral surface of the braiding 8. According toanother executive variation of the form, as an alternative to orcombined with the solution shown in FIGS. 2 or 3, it can be foreseenthat the outside lateral surface of the cylinder 1 is suitablycone-shaped in the portion which forms chamber C, or it can be foreseenthat the sock 8 is made with a differentiated elasticity in its length,so as to avoid that the sock 8, during its elastic contraction movement,blocks the openings 7, at least until the chamber C becomes empty.

[0011] If the sock 8 has to be used on shock absorbers or on telescopicsystems where it could be visible, some means can be provided for toprotect the sock itself, for instance by means of a flexible, possiblybellows-like sheath, made of any material suitable for this purpose.

[0012] With reference to FIGS. 4 and 5, the application of the discussedimprovements in one of the legs of a fork, in particular for mountainbikes, is now described, said fork consisting of two identical cushionedtelescopic legs, connected one to the other on their upper end by meansof cross pieces supporting the axis of the handlebar and supplied ontheir lower ends with attachments for their connection to the wheel hub.In such figures, the numeral 13 indicates the sheath or outer slidingtube, i.e., the tubular elements with the larger section of the leg,which is closed on its upper end by means of a plug 14 and in which thetubular stem 15 slides telescopically being closed on its lower end bymeans of a plug 16 and supplied with an extension 5 for connection tothe wheel axis. In the example shown, the sheath 13 is supplied on itsown lower end with a sealed closure system 17 and a guiding ring 117with an inside diameter smaller than the diameter of the sheath itself,said guiding ring containing the stem 15 with lateral seal slidingwithin itself, said stem being provided on its upper end with an outsidering 18 which slides with a lateral seal on the surface of the sheathitself, so that the sliding surface for the portions 13 and 15 islimited to the surface of the rings 117 and 18 and in such a way thatthere is a ring-shaped chamber D between the two portions, which is inconstant communication with the inside chamber E of the telescopicsystem 13, 15 through the openings 19 obtained on the upper end of thestem 15 under the sliding ring 18. The air space D can freely take in ordischarge air, through the holes 18 from or into the chamber E and itcan receive a small amount of oil for the lubrication of the relativelymovable surfaces of the parts 13 and 15 from said chamber E. The chamberE of the leg is partly occupied by lubricating oil, preferably of thehigh-density type, which can reach the openings 19 through the periodicoverturning of the fork and because of the emulsification of the oilitself with the air contained in the chamber E.

[0013] The plug 14 closes the end of the cylinder 1 of a shock absorberas described in FIG. 1, placed within the telescopic system 13, 15,coaxially with the stem 3 which may be oriented in the same direction asthe stem 15 and integral with the group formed by the plug 16 togetherwith the coupling 6. On the plug 16 adjusting means can be provided,which are not shown here since they are known in other types ofsuspensions manufactured by the applicant company and since they have noinfluence on the understanding of the present invention, to adjust thevalve means 6 placed on the piston 2 of the shock absorber. Otheradjusting means, which are not shown either can be provided on the plug14, whose purpose is to adjust possible valve means placed within thechamber A of the shock absorber, said means not being shown either,whose purpose is to adjust the position of the fork formed by said legs,during both the compression and the

[0014] extension stage. The fork shaft also contains the holes 7together with the outside ring-shaped recess 107 on the upper end of thecylinder 1 and the impermeable, flexible and elastic braiding 8 outsidesaid cylinder 1, fastened with its ends onto said cylinder by means ofthe clamping elements 9 and 10. The braiding is shaped in such a way asnot to interfere with the upper end of the sheath 15 of the telescopicshaft. The chambers A, B and C of the shock absorber are full of a lowviscosity liquid, which is sufficiently stable to changes in the forkoperating temperature. Thanks to the diaphragm 8 the lubricating oillocated in chamber E of the telescopic system 13, 15 will never mix withthe oil in the loop of the shock absorber. An elastic means 20consisting for instance of a spring or of a group of elastomer elementsis provided within the stem 15, outside the stem 3 of the shockabsorber, bearing with one end onto the bottom of the stem 15 and withthe other end onto a cup 101 of the cylinder 1, so as to urge toextension the fork log. It is understood that the fork shaft shown inFIGS. 4 and 5 can also be reversed, that is to say, with the stem 15oriented upwards and connected to the bike handlebar and with the sheath13 oriented downwards and connected to the wheel axis of the bikeitself, thus resulting in a better lubrication of thin portions 13, 15,even with a small amount of oil within the chamber E. It is alsounderstood that the shock absorber equipped with the compensator can befitted into the telescopic system 13, 15 with a reversed orientationwith respect to the orientation shown in FIGS. 4 and 5. Finally, it isevident how the pressure within chamber E of this fork improves theelastic recovery of the braiding 8 and how it can even allow the use ofa braiding whose only feature is flexibility.

[0015] Therefore, it is obvious that the description has referred to apreferred embodiment of the present invention, which may undergo aplurality of variations and changes, particularly in its realization,without however departing from the informing principle of the invention,as described above, as shown and as claimed below. In the claims, thereferences in brackets are merely indicative and non-limiting of theprotection area of the claims themselves.

1. Hydraulic or hydra pneumatic shock absorber or telescopic suspension,equipped with built-in compensator, including a cylinder full of oil,closed on one end, which is usually arranged for the connection to apoint of the mechanism to be cushioned, and traversed at the other endwith lateral seal by a stem connected with its outside and to the secondpoint of the mechanism to be cushioned, whereas said stem, with itsother end, is fastened to a piston running with lateral seal within thecylinder and supporting valve means to check the oil flow between thetwo inside chambers of the cylinder when the stem is moved to itsextended or retracted positions while a compensator provides for thecompensation of the various volume changes in said chambers,characterized in that the compensator consists of at least one flexible,impermeable and chemically oil-resistant braiding, fitted up so as towrap up said cylinder in its whole length or part of it, seal-fastenedwith its own ends onto said cylinder by means of suitable clamping meansand forming, with the cylinder itself, an auxiliary chamber withchanging volume, occupied by oil and communicating by means of holesprovided on the cylinder with at least one of the inside chambers of thecylinder itself, for instance the chamber with the larger volume, so asto compensate the various volume changes in such chambers while theshock absorber is working.
 2. Shock absorber according to claim 1, inwhich the braiding is flexible and elastic and it consists, forinstance, of at least one pipe made of a suitable elastomeric material.3. Shock absorber according to the previous claims, in which thebraiding made of elastomeric material can be coated with a flexiblesheath made of any suitable protective material, eventuallybellows-like.
 4. Shock absorber according to claim 1, in which thefastenings means of the ends of the braiding to the cylinder arecentripetal clamping means, for instance bands, hoops or ringssurmounted by other rings, with cone-shaped coupling andanti-unthreading flutes.
 5. Shock absorber according to the previousclaims, in which the ends of the braiding and/or the cylinder portionsonto which said ends of the braiding bear can be profiled in anysuitable way so as to ensure the best co-operation of the braidingitself, also as far as sealing is concerned, with the fastening meansand/or with the supporting cylinder.
 6. Shock absorber according toclaim 1, in which the holes through which the compensation chambercommunicates with the inside circuit of the shock absorber itself, areplaced on one end of said chamber and located within a ring-shapedrecess of the cylinder.
 7. Shock absorber according to claim 6, in whichat said ring-shaped recess there open the ends of small longitudinalgrooves occupying the whole length or part of the cylinder portionwrapped up into the expansion braiding.
 8. Shock absorber according toclaim 7, in which said longitudinal grooves can be provided on theinside lateral surface of the braiding.
 9. Shock absorber according toclaim 2, in which the elastic expansion braiding shows a differentelasticity in its length.
 10. Shock absorber according to claim 2, inwhich the surface portion of the cylinder onto which the braiding isfitted up can suitably be cone-shaped.
 11. Shock absorber according tothe previous claims, characterized in that it is fitted up within asheath and a stem, connected one to the other telescopically and formingthe fork leg of a mountain bike or any other two-wheel vehicle, with thecylinder fastened for instance to the end of the sheath and with thestem fastened for instance to the end of the stem of said fork shaft andwith an elastic means, consisting for instance of a helicoidal spring orof elastomer elements, extending the whole system, so that thecompensation braiding is protected within the leg, the inside chamber orchambers of the leg itself being suitably pressurized with respect toatmospheric pressure and being equipped with a suitable amount oflubricating oil, with suitable features, which is kept separate from theoil in the inside loop of the shock absorber by means of said braiding.12. Hydraulic or hydropneumatic shock absorber or telescopic suspension,equipped with built-in compensator, having small overall dimensions,easy to carry out and highly reliable, constructed in particular,completely or substantially as described, as shown and for the aboveobjects.